US20070175865A1 - Process for the fabrication of an inertial sensor with failure threshold - Google Patents
Process for the fabrication of an inertial sensor with failure threshold Download PDFInfo
- Publication number
- US20070175865A1 US20070175865A1 US11/566,590 US56659006A US2007175865A1 US 20070175865 A1 US20070175865 A1 US 20070175865A1 US 56659006 A US56659006 A US 56659006A US 2007175865 A1 US2007175865 A1 US 2007175865A1
- Authority
- US
- United States
- Prior art keywords
- sample element
- forming
- substrate
- sample
- process according
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H1/00—Contacts
- H01H1/0036—Switches making use of microelectromechanical systems [MEMS]
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P1/00—Details of instruments
- G01P1/02—Housings
- G01P1/023—Housings for acceleration measuring devices
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/04—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses for indicating maximum value
- G01P15/06—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses for indicating maximum value using members subjected to a permanent deformation
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P15/0802—Details
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P15/0891—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values with indication of predetermined acceleration values
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/18—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration in two or more dimensions
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P2015/0805—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration
- G01P2015/0808—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining in-plane movement of the mass, i.e. movement of the mass in the plane of the substrate
- G01P2015/0811—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining in-plane movement of the mass, i.e. movement of the mass in the plane of the substrate for one single degree of freedom of movement of the mass
- G01P2015/0814—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining in-plane movement of the mass, i.e. movement of the mass in the plane of the substrate for one single degree of freedom of movement of the mass for translational movement of the mass, e.g. shuttle type
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H35/00—Switches operated by change of a physical condition
- H01H35/14—Switches operated by change of acceleration, e.g. by shock or vibration, inertia switch
- H01H35/146—Switches operated by change of acceleration, e.g. by shock or vibration, inertia switch operated by plastic deformation or rupture of structurally associated elements
Definitions
- the present invention relates to a process for the fabrication of an inertial sensor with failure threshold.
- MEMS sensors are sensors that can be integrated in a semiconductor chip and are suitable for detecting various quantities.
- MEMS accelerometers with capacitive unbalancing are known.
- these accelerometers are normally provided with a fixed body and of a mobile mass, both of which are conductive and are capacitively coupled together.
- the capacitance present between the fixed body and the mobile mass may vary, and its value depends upon the relative position of the mobile mass with respect to the fixed body.
- the accelerometer is subjected to a stress, the mobile mass is displaced with respect to the fixed body and causes a variation in the coupling capacitance, which is detected by a special sensing circuit.
- MEMS accelerometers are extremely sensitive and precise; however, they are not suitable for being used in many applications, mainly because they are complex to make and their cost is very high.
- the processes of fabrication involve the execution of numerous non-standard steps and/or the use of non-standard substrates (for example, SOI substrates); on the other hand, it is normally necessary to provide feedback sensing circuits based upon differential charge amplifiers, the design of which frequently involves some difficulties.
- the purpose of the present invention is to provide a process for the fabrication of an inertial sensor with failure threshold, which will enable the problems described above to be overcome.
- a process for the fabrication of an inertial sensor with failure threshold, including the step of forming at least one sample element embedded in a sacrificial region on top of a substrate of a semiconductor wafer, the sample element being configured to fracture under a preselected force.
- the process further includes forming, on top of the sacrificial region, a body connected to the sample element, and etching the sacrificial region, so as to free the body and the sample element.
- the process may include the step of making a weakened region of the sample element.
- the weakened region may be made by forming a narrowed region or notches in the sample element.
- the process may include forming a plurality of sample elements, each configured to fracture under the preselected force.
- a method for manufacturing an inertial sensor comprising forming, on a semiconductor substrate, a sample element configured to break under a preselected strain, the sample element having a first end coupled to the substrate, and forming, above the semiconductor substrate, a semiconductor material body coupled to a second end of the sample element.
- the method may include forming a weakened region on the sample element, with the sample element configured to break at the weakened region under the preselected strain.
- the sample element may have a T shape, the first end being the cross-bar portion of the T and being coupled to the substrate at extreme ends thereof, the second end being the upright portion of the T.
- the method may also include forming an additional sample element having a first end coupled to the substrate, a second end coupled to the semiconductor material body, and configured to break under the preselected strain.
- a method of measuring movement of a device including providing a circuit in the device configured to permanently change the conductive state of a conductive path in the event the device is subjected to an acceleration exceeding a preselected level, applying a potential at first and second ends of the conductive path, and detecting a change in the conductive state of the conductive path.
- the method may further include breaking a semiconductor structure through which the conductive path passes in the event the device is subjected to the acceleration. This step may be performed by moving a first semiconductor body relative to a second semiconductor body in response to inertial forces resulting from the acceleration, the semiconductor structure being coupled at a first end thereof to the first body and at a second end to the second body, the movement of the first body causing a flexion of the structure, resulting in the breaking thereof.
- the device may be a cell phone, and the preselected level may be selected to correspond to an acceleration caused by a drop of the device to an unyielding surface from a preselected height.
- the preselected level may also be selected to be equal to or less than an acceleration sufficient to damage the device.
- FIGS. 1 and 2 are cross-sectional views through a semiconductor wafer in successive steps of fabrication in a first embodiment of the process according to the present invention
- FIG. 3 is a top plan view of the wafer of FIG. 2 ;
- FIG. 4 illustrates an enlarged detail of FIG. 3 ;
- FIG. 5 is a cross-sectional view of the wafer of FIG. 3 in a subsequent fabrication step
- FIG. 6 is a top plan view of the wafer of FIG. 5 ;
- FIGS. 7 and 8 are cross-sectional views of the wafer of FIG. 6 in a subsequent fabrication step, taken along the planes of trace VII-VII and VIII-VIII, respectively, of FIG. 6 ;
- FIG. 9 is a top plan view of the wafer of FIG. 7 , in a subsequent fabrication step, in which an inertial sensor is obtained;
- FIGS. 10 and 11 are cross-sectional views of the wafer of FIG. 9 , taken along the planes of trace X-X and XI-XI, respectively, of FIG. 9 ;
- FIGS. 12 and 13 are cross-sectional views through a composite wafer and a die, respectively, obtained starting from the wafer of FIG. 9 ;
- FIG. 14 is a schematic view of the top three quarters of a device incorporating the die of FIG. 13 ;
- FIG. 15 is a schematic illustration of an inertial sensor of the type illustrated in FIGS. 9-13 in an operative configuration
- FIG. 16 is a detail of an inertial sensor obtained according to a variant of the first embodiment of the present process.
- FIG. 17 is a top plan view of an inertial sensor obtained according to a further variant of the first embodiment of the present process.
- FIG. 18 is a cross-sectional view of the sensor of FIG. 17 ;
- FIG. 19 is a top plan view of an inertial sensor obtained according to a second embodiment of the present invention.
- FIG. 20 illustrates an enlarged detail of FIG. 19 ;
- FIG. 21 is a top plan view of an inertial sensor obtained according to a third embodiment of the present invention.
- FIG. 22 illustrates an enlarged detail of FIG. 21 ;
- FIG. 23 is a schematic illustration of two inertial sensors of the type illustrated in FIG. 21 in an operative configuration
- FIG. 24 is a cross-sectional view through a semiconductor wafer in an initial fabrication step of a process according to a fourth embodiment of the present invention.
- FIG. 25 is a top plan view of the wafer of FIG. 24 ;
- FIG. 26 illustrates the wafer of FIG. 24 in a subsequent fabrication step
- FIG. 27 is a top plan view of the wafer of FIG. 26 in a subsequent fabrication step, in which an inertial sensor is obtained;
- FIG. 28 is a cross-sectional view through the wafer of FIG. 27 , taken according to the plane of trace XXVI-XXVI of FIG. 27 ;
- FIG. 29 is a plan view of a detail of an inertial sensor obtained according to a fifth embodiment of the present invention
- FIG. 30 is a side view of the detail of FIG. 29 ;
- FIG. 31 is a side view of the detail of FIG. 29 , obtained according to a variant of the fifth embodiment of the present invention.
- a wafer 1 of semiconductor material for example monocrystalline silicon, comprises a substrate 2 , on which a thin pad oxide layer 3 , for example 2.5 ⁇ m thick, is thermally grown.
- a conductive layer 5 of polysilicon having for example a thickness of between 400 and 800 nm and a dopant concentration of 10 19 atoms/cm 3 , is then deposited on the pad oxide layer 3 and is defined by means of a photolithographic process.
- Two T-shaped samples 6 are thus obtained, having respective feet 6 a, aligned with respect to one another and extending towards one another, and respective arms 6 b parallel to one another ( FIGS. 2-4 ).
- the first weakened region 9 and the second weakened region 10 are made as narrowed portions of the foot 6 a and, respectively, of one of the arms 6 b.
- the weakened regions 9 , 10 are defined by notches 11 with a circular or polygonal profile, made in an area of joining 6 c between the foot 6 a and the arms 6 b and traversing the sample 6 in a direction parallel to the third axis Z.
- the thickness of the conductive layer 5 of polysilicon, the dimensions of the feet 6 a and of the arms 6 b of the samples 6 , and the conformation of the weakened regions 9 , 10 determine the mechanical resistance to failure of the samples 6 themselves.
- a sacrificial layer 12 of silicon dioxide is deposited so as to coat the pad oxide layer 3 and the samples 6 .
- the pad oxide layer 3 and the sacrificial layer 12 form a single sacrificial region in which the samples 6 are embedded.
- the sacrificial layer 12 is then defined by means of a photolithographic process comprising two masking steps. During a first step, first openings 14 are made in the sacrificial layer 12 , exposing respective ends of the feet 6 a of the samples 6 , as illustrated in FIG. 5 . In a second step of the photolithographic process ( FIG. 6 ), both the sacrificial layer 12 and the pad oxide layer 3 are selectively etched, so as to make second openings 15 , exposing portions of the substrate 2 .
- the mobile mass 18 is connected to the substrate 2 by the springs 20 , which are in turn constrained to the anchorages 19 ( FIG. 11 ).
- the springs 20 which are per se known, are shaped so as to enable oscillations of the mobile mass 18 with respect to the substrate 2 along each of the three axes X, Y, Z, at the same time, however, preventing rotations.
- the mobile mass 18 is moreover constrained to the substrate 2 through the samples 6 .
- the mobile mass 18 has, in a median portion, a pair of anchoring blocks 22 , projecting outwards in opposite directions along the second axis Y.
- the anchoring blocks 22 are connected to the end of the foot 6 a of a respective one of the samples 6 , as illustrated in FIG. 10 .
- the samples 6 are anchored to the substrate 2 through the anchoring pads 8 .
- the silicon dioxide is in fact removed only partially underneath the anchoring pads 8 , which are wider than the feet 6 a and the arms 6 b of the samples 6 ; thus, residual portions 3 ′ of the pad oxide layer 3 , which are not etched, fix the anchoring pads 8 to the substrate 2 , serving as bonding elements.
- the mobile mass 18 is suspended at a distance on the substrate 2 and can oscillate about a resting position, in accordance with the degrees of freedom allowed by the springs 20 (in particular, it can translate along the axes X, Y and Z).
- the samples 6 are elastic elements, which connect the mobile mass 18 to the substrate 2 in a way similar to the springs 20 .
- the samples are shaped so as to be subjected to a stress when the mobile mass 18 is outside a relative resting position with respect to the substrate 2 .
- the samples 6 are, however, very thin and have preferential failure points in areas corresponding to the weakened regions 9 , 10 . For this reason, their mechanical resistance to failure is much lower than that of the springs 20 , and they undergo failure in a controlled way when they are subjected to a stress of pre-set intensity.
- the mobile mass 18 , the substrate 2 , the springs 20 with the anchorages 19 , and the samples 6 form an inertial sensor 24 , the operation of which will be described in detail hereinafter.
- the die 30 is finally mounted on a device 32 , for example a cell phone.
- the device 32 is provided with a casing 33 , inside which the die 30 is fixed, as illustrated in FIG. 14 .
- the inertial sensor 24 is connected to terminals of a testing circuit 35 , which measures the value of electrical resistance between said terminals.
- the anchoring pads 8 of the arms 6 b, in which the second weakened regions 10 are formed are connected each to a respective terminal of the testing circuit 35 .
- the samples 6 and the mobile mass 18 form a conductive path that enables passage of current between any given pair of anchoring pads 8 .
- the testing circuit 35 detects low values of electrical resistance between the anchoring pads 8 .
- the device 32 undergoes modest stresses, which cause slight oscillations of the mobile mass 18 about the resting position, without jeopardizing the integrity of the inertial sensor 24 .
- the mobile mass 18 of the inertial sensor 24 undergoes a sharp acceleration and subjects the samples 6 and the springs 20 to a force. According to the intensity of the stress transmitted to the inertial sensor 24 , said force can exceed one of the thresholds of mechanical failure of the samples 6 , which consequently break. In particular, failure occurs at one of the weakened regions 9 , 10 , which have minimum strength. In either case, the conductive path between the two anchoring pads 8 connected to the testing circuit 35 is interrupted, and hence the testing circuit detects a high value of electrical resistance between its own terminals, thus enabling recognition of the occurrence of events that are liable to damage the device 32 .
- the two T-shaped samples 6 are located in a gap 36 between the substrate 2 and the mobile mass 18 and have the end of the respective feet 6 a in mutual contact.
- both of the samples 6 are fixed to a single anchoring block 22 ′ set centrally with respect to the mobile mass 18 itself.
- inertial sensors with failure threshold are particularly suitable for use where it is necessary to record the occurrence of stresses that are harmful for a device in which they are incorporated and in which it is superfluous to provide precise measurements of accelerations.
- they can be advantageously used for verifying the validity of the warranty in the case of widely used electronic devices, such as, for example, cell phones.
- inertial sensors obtained using the process described are more advantageous because they respond in a substantially isotropic way to the mechanical stress. In practice, therefore, just one inertial sensor is sufficient to detect forces acting in any direction.
- the samples 41 have first ends connected to respective anchoring blocks 22 of the mobile mass 18 , and second ends terminating with respective anchoring pads 41 fixed to the substrate 2 , as explained previously.
- notches 42 made at respective vertices 43 of the samples 41 define weakened regions 44 of the samples 40 .
- FIGS. 21 and 22 illustrate a third embodiment of the invention, according to which an inertial sensor 50 is obtained, made on a substrate 54 and provided with substantially rectilinear samples 51 that extend parallel to the first axis X.
- an inertial sensor 50 is obtained, made on a substrate 54 and provided with substantially rectilinear samples 51 that extend parallel to the first axis X.
- two anchorages 52 and two springs 53 are provided, which connect the mobile mass 18 to the anchorages 52 and are shaped so as to prevent substantially the rotation of the mobile mass 18 itself about the first axis X.
- the weakened regions may be absent.
- the inertial sensor 50 responds preferentially to stresses oriented according to a plane orthogonal to the samples 51 , i.e., the plane defined by the second axis Y and by the third axis Z.
- a plane orthogonal to the samples 51 i.e., the plane defined by the second axis Y and by the third axis Z.
- a pad oxide layer 62 is grown on a semiconductor wafer 60 having a substrate 61 .
- a conductive layer 63 of polycrystalline silicon (here indicated by a dashed line) is deposited on the pad oxide layer 61 and is defined to form a sample 64 , which is substantially rectilinear and extends parallel to the first axis X ( FIG. 25 ).
- the sample 64 has an anchoring pad 65 at one of its ends and has a weakened region 66 defined by a pair of notches 67 in a central position.
- a sacrificial layer 69 of silicon dioxide is deposited so as to coat the entire wafer 60 and is then selectively removed to form an opening 68 at one end of the sample 64 opposite to the anchoring pad 65 .
- An epitaxial layer 70 is then grown ( FIG. 26 ), which is etched so as to form a mobile mass 71 , anchorages 72 , springs 73 , and a supporting ring (not illustrated for reasons of convenience).
- the epitaxial layer extends into the opening 68 to form a connection region 88 between the sample 64 and the mobile mass 71 .
- the sacrificial layer 69 and the pad oxide layer 62 are removed, except for a residual portion 62 ′ of the pad oxide layer 62 underlying the anchoring pad 65 ( FIGS. 27 and 28 ). The mobile mass 71 and the sample 64 are thus freed.
- an inertial sensor 80 is obtained, which is then encapsulated through steps similar to the ones described with reference to FIGS. 12 and 13 .
- the use of a single anchoring point between the sample and the mobile mass advantageously enables effective relaxation of the stresses due to expansion of the mobile mass.
- the sample is T-shaped, like the ones illustrated in FIG. 9 .
- FIG. 29 illustrates a detail of a sample 81 , for example a rectilinear one, of an inertial sensor obtained using a fifth embodiment of the process according to the invention.
- the sample 81 has a weakened region defined by a transverse groove 82 extending between opposite sides 83 of the sample 81 .
- the groove 82 is obtained by means of masked etching of controlled duration of the sample 81 ( FIG. 30 ).
- a first layer 85 of polysilicon is deposited and defined. Then, a stop layer 86 of silicon dioxide and a second layer 87 of polysilicon are formed. Finally, a groove 82 ′ is dug by etching the second layer 87 of polysilicon as far as the stop layer 86 .
- the weakened regions can be defined by using side notches in the samples together with grooves extending between the side notches.
- the weakened regions could be defined by through openings that traverse the samples, instead of by side notches.
Abstract
A process for the fabrication of an inertial sensor with failure threshold includes the step of forming, on top of a substrate of a semiconductor wafer, a sample element embedded in a sacrificial region, the sample element configured to break under a preselected strain. The process further includes forming, on top of the sacrificial region, a body connected to the sample element and etching the sacrificial region so as to free the body and the sample element. The process may also include forming, on the substrate, additional sample elements connected to the body.
Description
- 1. Field of the Invention
- The present invention relates to a process for the fabrication of an inertial sensor with failure threshold.
- 2. Description of the Related Art
- As is known, modern techniques of micromachining of semiconductors can be advantageously exploited for making various extremely sensitive and precise sensors, having further small overall dimensions. The so-called MEMS sensors (or micro-electro-mechanical-system sensors), are sensors that can be integrated in a semiconductor chip and are suitable for detecting various quantities. In particular, both linear and rotational MEMS accelerometers with capacitive unbalancing are known. In brief, these accelerometers are normally provided with a fixed body and of a mobile mass, both of which are conductive and are capacitively coupled together. In addition, the capacitance present between the fixed body and the mobile mass may vary, and its value depends upon the relative position of the mobile mass with respect to the fixed body. When the accelerometer is subjected to a stress, the mobile mass is displaced with respect to the fixed body and causes a variation in the coupling capacitance, which is detected by a special sensing circuit.
- As mentioned previously, MEMS accelerometers are extremely sensitive and precise; however, they are not suitable for being used in many applications, mainly because they are complex to make and their cost is very high. On the one hand, in fact, the processes of fabrication involve the execution of numerous non-standard steps and/or the use of non-standard substrates (for example, SOI substrates); on the other hand, it is normally necessary to provide feedback sensing circuits based upon differential charge amplifiers, the design of which frequently involves some difficulties.
- In addition, in many cases the precision of capacitive MEMS sensors is not required and, indeed, it is not even necessary to have an instantaneous measurement of the value of acceleration. On the contrary, it is frequently just necessary to verify whether a device incorporating the accelerometer has undergone accelerations higher than a pre-set threshold, normally on account of impact. For example, the majority of electronic devices commonly used, such as cell phones, are protected by a warranty, which, however, is no longer valid if any malfunctioning is due not to defects of fabrication but to an impact consequent on the device being dropped onto an unyielding surface or in any case on a use that is not in conformance with the instructions. Unless visible damage is found, such as marks on the casing or breaking of some parts, it is practically impossible to demonstrate that the device has suffered damage that invalidates the warranty. On the other hand, portable devices, such as cell phones, exactly, are particularly exposed to being dropped and consequently to getting broken, precisely on account of how they are used.
- Events of the above type could be easily detected by an inertial sensor, which is able to record accelerations higher than a pre-set threshold. However, the use of MEMS accelerometers of a capacitive type in these cases would evidently lead to excessive costs. It would thus be desirable to have available sensors that can be made using techniques of micromachining of semiconductors, consequently having overall dimensions comparable to those of capacitive MEMS sensors, but simpler as regards both the structure of the sensor and the sensing circuit. In addition, also the processes of fabrication should be, as a whole, simple and inexpensive.
- The purpose of the present invention is to provide a process for the fabrication of an inertial sensor with failure threshold, which will enable the problems described above to be overcome.
- According to an embodiment of the present invention, a process is provided for the fabrication of an inertial sensor with failure threshold, including the step of forming at least one sample element embedded in a sacrificial region on top of a substrate of a semiconductor wafer, the sample element being configured to fracture under a preselected force. The process further includes forming, on top of the sacrificial region, a body connected to the sample element, and etching the sacrificial region, so as to free the body and the sample element.
- The process may include the step of making a weakened region of the sample element. The weakened region may be made by forming a narrowed region or notches in the sample element.
- The process may include forming a plurality of sample elements, each configured to fracture under the preselected force.
- According to an alternative embodiment of the invention, a method for manufacturing an inertial sensor is provided, comprising forming, on a semiconductor substrate, a sample element configured to break under a preselected strain, the sample element having a first end coupled to the substrate, and forming, above the semiconductor substrate, a semiconductor material body coupled to a second end of the sample element. The method may include forming a weakened region on the sample element, with the sample element configured to break at the weakened region under the preselected strain.
- According to this embodiment, the sample element may have a T shape, the first end being the cross-bar portion of the T and being coupled to the substrate at extreme ends thereof, the second end being the upright portion of the T.
- The method may also include forming an additional sample element having a first end coupled to the substrate, a second end coupled to the semiconductor material body, and configured to break under the preselected strain.
- According to another embodiment of the invention, A method of measuring movement of a device is provided, including providing a circuit in the device configured to permanently change the conductive state of a conductive path in the event the device is subjected to an acceleration exceeding a preselected level, applying a potential at first and second ends of the conductive path, and detecting a change in the conductive state of the conductive path.
- The method may further include breaking a semiconductor structure through which the conductive path passes in the event the device is subjected to the acceleration. This step may be performed by moving a first semiconductor body relative to a second semiconductor body in response to inertial forces resulting from the acceleration, the semiconductor structure being coupled at a first end thereof to the first body and at a second end to the second body, the movement of the first body causing a flexion of the structure, resulting in the breaking thereof.
- The device may be a cell phone, and the preselected level may be selected to correspond to an acceleration caused by a drop of the device to an unyielding surface from a preselected height. The preselected level may also be selected to be equal to or less than an acceleration sufficient to damage the device.
- For a better understanding of the invention, some embodiments thereof are now described, purely by way of non-limiting examples and with reference to the attached drawings, in which:
-
FIGS. 1 and 2 are cross-sectional views through a semiconductor wafer in successive steps of fabrication in a first embodiment of the process according to the present invention; -
FIG. 3 is a top plan view of the wafer ofFIG. 2 ; -
FIG. 4 illustrates an enlarged detail ofFIG. 3 ; -
FIG. 5 is a cross-sectional view of the wafer ofFIG. 3 in a subsequent fabrication step; -
FIG. 6 is a top plan view of the wafer ofFIG. 5 ; -
FIGS. 7 and 8 are cross-sectional views of the wafer ofFIG. 6 in a subsequent fabrication step, taken along the planes of trace VII-VII and VIII-VIII, respectively, ofFIG. 6 ; -
FIG. 9 is a top plan view of the wafer ofFIG. 7 , in a subsequent fabrication step, in which an inertial sensor is obtained; -
FIGS. 10 and 11 are cross-sectional views of the wafer ofFIG. 9 , taken along the planes of trace X-X and XI-XI, respectively, ofFIG. 9 ; -
FIGS. 12 and 13 are cross-sectional views through a composite wafer and a die, respectively, obtained starting from the wafer ofFIG. 9 ; -
FIG. 14 is a schematic view of the top three quarters of a device incorporating the die ofFIG. 13 ; -
FIG. 15 is a schematic illustration of an inertial sensor of the type illustrated inFIGS. 9-13 in an operative configuration; -
FIG. 16 is a detail of an inertial sensor obtained according to a variant of the first embodiment of the present process; -
FIG. 17 is a top plan view of an inertial sensor obtained according to a further variant of the first embodiment of the present process; -
FIG. 18 is a cross-sectional view of the sensor ofFIG. 17 ; -
FIG. 19 is a top plan view of an inertial sensor obtained according to a second embodiment of the present invention; -
FIG. 20 illustrates an enlarged detail ofFIG. 19 ; -
FIG. 21 is a top plan view of an inertial sensor obtained according to a third embodiment of the present invention; -
FIG. 22 illustrates an enlarged detail ofFIG. 21 ; -
FIG. 23 is a schematic illustration of two inertial sensors of the type illustrated inFIG. 21 in an operative configuration; -
FIG. 24 is a cross-sectional view through a semiconductor wafer in an initial fabrication step of a process according to a fourth embodiment of the present invention; -
FIG. 25 is a top plan view of the wafer ofFIG. 24 ; -
FIG. 26 illustrates the wafer ofFIG. 24 in a subsequent fabrication step; -
FIG. 27 is a top plan view of the wafer ofFIG. 26 in a subsequent fabrication step, in which an inertial sensor is obtained; -
FIG. 28 is a cross-sectional view through the wafer ofFIG. 27 , taken according to the plane of trace XXVI-XXVI ofFIG. 27 ; -
FIG. 29 is a plan view of a detail of an inertial sensor obtained according to a fifth embodiment of the present invention -
FIG. 30 is a side view of the detail ofFIG. 29 ; and -
FIG. 31 is a side view of the detail ofFIG. 29 , obtained according to a variant of the fifth embodiment of the present invention. - With reference to
FIGS. 1-13 , awafer 1 of semiconductor material, for example monocrystalline silicon, comprises asubstrate 2, on which a thinpad oxide layer 3, for example 2.5 μm thick, is thermally grown. Aconductive layer 5 of polysilicon, having for example a thickness of between 400 and 800 nm and a dopant concentration of 1019 atoms/cm3, is then deposited on thepad oxide layer 3 and is defined by means of a photolithographic process. Two T-shapedsamples 6 are thus obtained, havingrespective feet 6 a, aligned with respect to one another and extending towards one another, andrespective arms 6 b parallel to one another (FIGS. 2-4 ). Thefeet 6 a and thearms 6 b of eachsample 6 are set in directions identified by a first axis X and, respectively, by a second axis Y, which are mutually orthogonal (a third axis Z, orthogonal to the first axis X and the second axis Y, is illustrated inFIG. 2 ). In addition, at respective ends of thearms 6 b of both thesamples 6anchoring pads 8 are made, of a substantially rectangular shape and having a width greater than thearms 6 b. As illustrated inFIG. 4 , each of thesamples 6 has a first weakened region 9 and a second weakenedregion 10. In particular, in both of thesamples 6, the first weakened region 9 and the second weakenedregion 10 are made as narrowed portions of thefoot 6 a and, respectively, of one of thearms 6 b. In addition, the weakenedregions 9, 10 are defined bynotches 11 with a circular or polygonal profile, made in an area of joining 6 c between thefoot 6 a and thearms 6 b and traversing thesample 6 in a direction parallel to the third axis Z. The thickness of theconductive layer 5 of polysilicon, the dimensions of thefeet 6 a and of thearms 6 b of thesamples 6, and the conformation of the weakenedregions 9, 10 determine the mechanical resistance to failure of thesamples 6 themselves. In particular, acting on the shape and on the dimensions of thenotches 11 defining the first weakened region 9 and the second weakenedregion 10, it is possible to obtain pre-set failure thresholds of thesamples 6 along the first, second and third axes X, Y and Z. Preferably, all the mechanical failure thresholds are basically the same. - Next, a
sacrificial layer 12 of silicon dioxide is deposited so as to coat thepad oxide layer 3 and thesamples 6. In practice, thepad oxide layer 3 and thesacrificial layer 12 form a single sacrificial region in which thesamples 6 are embedded. Thesacrificial layer 12 is then defined by means of a photolithographic process comprising two masking steps. During a first step,first openings 14 are made in thesacrificial layer 12, exposing respective ends of thefeet 6 a of thesamples 6, as illustrated inFIG. 5 . In a second step of the photolithographic process (FIG. 6 ), both thesacrificial layer 12 and thepad oxide layer 3 are selectively etched, so as to makesecond openings 15, exposing portions of thesubstrate 2. - Subsequently, a
conductive epitaxial layer 16 is grown on thewafer 1, the said layer having a thickness, for example, of 15 μm and a dopant concentration of 1018 atoms/cm3. In detail, theepitaxial layer 16 coats thesacrificial layer 12 entirely and extends in depth through the first and thesecond openings samples 6 and thesubstrate 2, respectively, are reached (FIGS. 7 and 8 ). - The
epitaxial layer 16 is then selectively etched, preferably by reactive-ion etching (RIE), and thesacrificial layer 12 and thepad oxide layer 3 are removed. In greater detail, during the step of etching of theepitaxial layer 16, the following are formed: amobile mass 18;anchorages 19, provided on the portions of thesubstrate 2 previously exposed by thesecond openings 15; a plurality ofsprings 20, connecting themobile mass 18 to theanchorages 19; and a ring-shaped supportingstructure 21, which surrounds themobile mass 18, thesamples 6, thesprings 20, and the corresponding anchorages 19 (seeFIG. 9 , in which thesacrificial layer 12 and thepad oxide layer 3 have already been removed). - The
mobile mass 18 is connected to thesubstrate 2 by thesprings 20, which are in turn constrained to the anchorages 19 (FIG. 11 ). Thesprings 20, which are per se known, are shaped so as to enable oscillations of themobile mass 18 with respect to thesubstrate 2 along each of the three axes X, Y, Z, at the same time, however, preventing rotations. Themobile mass 18 is moreover constrained to thesubstrate 2 through thesamples 6. In greater detail, themobile mass 18 has, in a median portion, a pair of anchoring blocks 22, projecting outwards in opposite directions along the second axis Y. The anchoring blocks 22 are connected to the end of thefoot 6 a of a respective one of thesamples 6, as illustrated inFIG. 10 . In turn, thesamples 6 are anchored to thesubstrate 2 through theanchoring pads 8. By controlling the duration of etching of thesacrificial layer 12 and of thepad oxide layer 3, the silicon dioxide is in fact removed only partially underneath theanchoring pads 8, which are wider than thefeet 6 a and thearms 6 b of thesamples 6; thus,residual portions 3′ of thepad oxide layer 3, which are not etched, fix theanchoring pads 8 to thesubstrate 2, serving as bonding elements. - The
sacrificial layer 12 and the remaining portions of thepad oxide layer 3 are, instead, completely removed and, hence, themobile mass 18 and thesamples 6 are freed. In practice, themobile mass 18 is suspended at a distance on thesubstrate 2 and can oscillate about a resting position, in accordance with the degrees of freedom allowed by the springs 20 (in particular, it can translate along the axes X, Y and Z). Also thesamples 6 are elastic elements, which connect themobile mass 18 to thesubstrate 2 in a way similar to thesprings 20. In particular, the samples are shaped so as to be subjected to a stress when themobile mass 18 is outside a relative resting position with respect to thesubstrate 2. Thesamples 6 are, however, very thin and have preferential failure points in areas corresponding to the weakenedregions 9, 10. For this reason, their mechanical resistance to failure is much lower than that of thesprings 20, and they undergo failure in a controlled way when they are subjected to a stress of pre-set intensity. - In practice, at this stage of the process, the
mobile mass 18, thesubstrate 2, thesprings 20 with theanchorages 19, and thesamples 6 form aninertial sensor 24, the operation of which will be described in detail hereinafter. - An
encapsulation structure 25 for theinertial sensor 24 is then applied on top of thewafer 1, forming a composite wafer 26 (FIG. 12 ). In particular, theencapsulation structure 25 is an additional semiconductor wafer, in which arecess 27 has previously been opened, in a region that is to be laid on top of themobile mass 18. Theencapsulation structure 25 is coupled to the ring-shaped supportingstructure 21 by the interposition of a layer ofsoldering 29. Next, thecompound wafer 26 is cut into a plurality ofdice 30, each die comprising aninertial sensor 24 and a respectiveprotective cap 31, formed by the fractioning of the encapsulation structure 25 (FIG. 13 ). - The
die 30 is finally mounted on adevice 32, for example a cell phone. Preferably, thedevice 32 is provided with acasing 33, inside which thedie 30 is fixed, as illustrated inFIG. 14 . In addition (FIG. 15 ), theinertial sensor 24 is connected to terminals of atesting circuit 35, which measures the value of electrical resistance between said terminals. In greater detail, theanchoring pads 8 of thearms 6 b, in which the second weakenedregions 10 are formed, are connected each to a respective terminal of thetesting circuit 35. - In normal conditions, i.e., when the
inertial sensor 24 is intact, thesamples 6 and themobile mass 18 form a conductive path that enables passage of current between any given pair ofanchoring pads 8. In practice, thetesting circuit 35 detects low values of electrical resistance between theanchoring pads 8. During normal use, thedevice 32 undergoes modest stresses, which cause slight oscillations of themobile mass 18 about the resting position, without jeopardizing the integrity of theinertial sensor 24. - When the
device 32 suffers a shock, themobile mass 18 of theinertial sensor 24 undergoes a sharp acceleration and subjects thesamples 6 and thesprings 20 to a force. According to the intensity of the stress transmitted to theinertial sensor 24, said force can exceed one of the thresholds of mechanical failure of thesamples 6, which consequently break. In particular, failure occurs at one of the weakenedregions 9, 10, which have minimum strength. In either case, the conductive path between the twoanchoring pads 8 connected to thetesting circuit 35 is interrupted, and hence the testing circuit detects a high value of electrical resistance between its own terminals, thus enabling recognition of the occurrence of events that are liable to damage thedevice 32. - According to a variant of the embodiment described, shown in
FIG. 16 , T-shapedsamples 37 are provided, which present a single weakenedregion 38. In particular, the weakenedregion 38 is a narrowed portion defined by a pair ofnotches 39, which are oblique with respect to afoot 37 a andarms 37 b of thesamples 37. - According to a further variant, illustrated in
FIGS. 17 and 18 , the two T-shapedsamples 6 are located in agap 36 between thesubstrate 2 and themobile mass 18 and have the end of therespective feet 6 a in mutual contact. In addition, both of thesamples 6 are fixed to asingle anchoring block 22′ set centrally with respect to themobile mass 18 itself. - The process according to the invention has the following advantages. In the first place, for fabrication of the
inertial sensor 24, processing steps that are standard in the microelectronics industry are employed. In particular, the following steps are carried out: steps of deposition of both insulating and conductive layers of material; photolithographic processes; a step of epitaxial growth; and standard steps of etching of the epitaxial silicon and of the insulating layers. Advantageously, a single step of thermal oxidation is carried out, and consequently thewafer 1 is subjected to modest stresses during the fabrication process. The yield of the process is therefore high. In addition, theinertial sensor 24 is obtained starting from a standard, low-cost substrate. - The process described consequently enables inertial sensors with failure threshold to be produced at a very low cost. Such sensors are particularly suitable for use where it is necessary to record the occurrence of stresses that are harmful for a device in which they are incorporated and in which it is superfluous to provide precise measurements of accelerations. For example, they can be advantageously used for verifying the validity of the warranty in the case of widely used electronic devices, such as, for example, cell phones.
- In addition, the inertial sensors provided with the present method have contained overall dimensions. In inertial sensors, in fact, large dimensions are generally due to the mobile mass, which must ensure the necessary precision and sensitivity. In this case, instead, it is sufficient that, in the event of a predetermined acceleration, the mobile mass will cause breaking of the weakened regions of the samples, which have low strength. It is consequently evident that also the mobile mass can have contained overall dimensions.
- The use of a single anchoring point between the samples and the mobile mass, as illustrated in the second variant of
FIGS. 17 and 18 , has a further advantage as compared to the ones already pointed out, because it enables more effective relaxation of the stresses due to expansion of the materials. In particular, it may happen that the polysilicon parts which are even only partially embedded in the silicon dioxide (samples and portions of the epitaxial layer) will be subjected to a compressive force, since both the polysilicon, and the oxide tend to a expand in opposite directions during the fabrication process. When the oxide is removed, the action of compression on the polysilicon is eliminated, and the polysilicon can thus expand. Clearly, the largest expansion, in absolute terms, is that of the mobile mass, since it has the largest size. The use of a single anchoring point, instead of two anchorages set at a distance apart enables more effective relaxation of the stresses due to said expansion, since the mobile mass can expand freely, without modifying the load state of the samples. - The inertial sensors obtained using the process described are more advantageous because they respond in a substantially isotropic way to the mechanical stress. In practice, therefore, just one inertial sensor is sufficient to detect forces acting in any direction.
- A second embodiment of the invention is illustrated in
FIGS. 19 and 20 , where parts that are the same as the ones already illustrated are designated by the same reference numbers. According to said embodiment, aninertial sensor 40 is made, having L-shapedsamples 41. As in the previous case, thesamples 41 are obtained by shaping a conductive polysilicon layer deposited on top of a pad oxide layer (not illustrated herein), which has in turn been grown on thesubstrate 42 of asemiconductor wafer 43. Using processing steps similar to the ones already described, themobile mass 18, theanchorages 19 and thesprings 20 are subsequently obtained. - In detail, the
samples 41 have first ends connected to respective anchoring blocks 22 of themobile mass 18, and second ends terminating withrespective anchoring pads 41 fixed to thesubstrate 2, as explained previously. In addition,notches 42 made atrespective vertices 43 of thesamples 41 define weakenedregions 44 of thesamples 40. -
FIGS. 21 and 22 illustrate a third embodiment of the invention, according to which aninertial sensor 50 is obtained, made on asubstrate 54 and provided with substantiallyrectilinear samples 51 that extend parallel to the first axis X. In this case, during the RIE etching step, in addition to themobile mass 18, twoanchorages 52 and twosprings 53 of a known type are provided, which connect themobile mass 18 to theanchorages 52 and are shaped so as to prevent substantially the rotation of themobile mass 18 itself about the first axis X. - The
samples 51 have first ends soldered to respective anchoring blocks 22 of themobile mass 18 and second ends terminating with anchoringpads 55, made as described previously. In addition, pairs of transverseopposed notches 57 define respective weakenedregions 58 along the samples 51 (FIG. 22 ). - Alternatively, the weakened regions may be absent.
- The
inertial sensor 50 responds preferentially to stresses oriented according to a plane orthogonal to thesamples 51, i.e., the plane defined by the second axis Y and by the third axis Z. In this case, to detect stresses in a substantially isotropic way, it is possible to use twosensors 50 connected in series between the terminals of atesting circuit 59 and rotated through 900 with respect to one another, as illustrated inFIG. 23 . - With reference to
FIGS. 24-28 , according to a fourth embodiment of the invention, apad oxide layer 62 is grown on asemiconductor wafer 60 having asubstrate 61. Next, aconductive layer 63 of polycrystalline silicon (here indicated by a dashed line) is deposited on thepad oxide layer 61 and is defined to form asample 64, which is substantially rectilinear and extends parallel to the first axis X (FIG. 25 ). Thesample 64 has ananchoring pad 65 at one of its ends and has a weakenedregion 66 defined by a pair ofnotches 67 in a central position. - A
sacrificial layer 69 of silicon dioxide is deposited so as to coat theentire wafer 60 and is then selectively removed to form anopening 68 at one end of thesample 64 opposite to theanchoring pad 65. - An
epitaxial layer 70 is then grown (FIG. 26 ), which is etched so as to form amobile mass 71,anchorages 72, springs 73, and a supporting ring (not illustrated for reasons of convenience). The epitaxial layer extends into theopening 68 to form aconnection region 88 between thesample 64 and themobile mass 71. Thesacrificial layer 69 and thepad oxide layer 62 are removed, except for aresidual portion 62′ of thepad oxide layer 62 underlying the anchoring pad 65 (FIGS. 27 and 28 ). Themobile mass 71 and thesample 64 are thus freed. More precisely, themobile mass 71, which has, at its center, a through opening 74 on top of thesample 64, is constrained to thesubstrate 61 through theanchorages 72 and thesprings 73, which are shaped so as to prevent any translation along or rotation about the first axis X. In addition, thesample 65 has opposite ends, one connected to thesubstrate 2 through theanchoring pad 65, and the other to themobile mass 71 atconnection region 88, and is placed in agap 76 comprised between themobile mass 71 and thesubstrate 61. - In this way, an
inertial sensor 80 is obtained, which is then encapsulated through steps similar to the ones described with reference toFIGS. 12 and 13 . - Also in this case, the use of a single anchoring point between the sample and the mobile mass advantageously enables effective relaxation of the stresses due to expansion of the mobile mass.
- According to one variant (not illustrated), the sample is T-shaped, like the ones illustrated in
FIG. 9 . -
FIG. 29 illustrates a detail of asample 81, for example a rectilinear one, of an inertial sensor obtained using a fifth embodiment of the process according to the invention. In particular, thesample 81 has a weakened region defined by atransverse groove 82 extending betweenopposite sides 83 of thesample 81. - The
groove 82 is obtained by means of masked etching of controlled duration of the sample 81 (FIG. 30 ). - Alternatively (
FIG. 31 ), afirst layer 85 of polysilicon is deposited and defined. Then, astop layer 86 of silicon dioxide and asecond layer 87 of polysilicon are formed. Finally, agroove 82′ is dug by etching thesecond layer 87 of polysilicon as far as thestop layer 86. - Finally, it is evident that modifications and variations may be made to the process described herein, without thereby departing from the scope of the present invention. In particular, the weakened regions can be defined by using side notches in the samples together with grooves extending between the side notches. In addition, the weakened regions could be defined by through openings that traverse the samples, instead of by side notches.
- All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety.
- From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.
Claims (30)
1. A process for the fabrication of an inertial sensor with failure threshold, comprising the steps of:
forming, on top of a substrate of a semiconductor wafer, at least one sample element embedded in a sacrificial region;
forming, on top of said sacrificial region, a body connected to said sample element; and
etching said sacrificial region, so as to free said body and said sample element, said sample element being breakable, following etching of said sacrificial region, when subjected to a preselected strain.
2. The process according to claim 1 , in which the step of forming said sample element comprises:
forming a first layer of a first material, which coats said substrate;
forming a second layer of a second material, which coats said first layer;
shaping said second layer, so as to define said sample element; and
forming a third layer of said first material coating said first layer and said sample element.
3. The process according to claim 2 , in which said first material is a dielectric material and said second material is a conductive material.
4. The process according to claim 3 , in which said first material is silicon dioxide and said second material is polysilicon.
5. The process according to claim 1 wherein the step of forming at least one sample element comprises the step of making at least one weakened region of said sample element.
6. The process according to claim 5 , in which the step of making at least one weakened region comprises the step of defining a narrowing of said sample element.
7. The process according to claim 6 in which said step of defining a narrowing portion comprises forming notches in edges of said sample element.
8. The process according to claim 5 in which the step of making at least one weakened region comprises making a groove in a surface of said sample element and extending between opposite edges of said sample element.
9. The process according to claim 8 , in which the step of making a groove comprises performing an etch of controlled duration of said sample element.
10. The process according to claim 8 in which the step of making a groove comprises:
forming a stop layer inside said sample element; and
etching said sample element until said stop element is reached.
11. The process according to claim 1 wherein the step of forming at least one sample element comprises defining at least one anchoring pad of said sample element.
12. The process according to claim 11 , in which the step of etching said sacrificial region is interrupted before removing residual portions of said sacrificial region underlying said anchoring pad.
13. The process according to claim 1 , further comprising making, before performing the step of forming said body, at least one first opening through said sacrificial region, which exposes one end of said sample element, and making second openings, which expose respective portions of said substrate.
14. The process according to claim 13 , in which the step of forming said body comprises:
growing an epitaxial layer, which extends on top of said sacrificial region and through said first opening and said second openings; and
etching said epitaxial layer until said sacrificial region is reached.
15. The process according to claim 14 , in which, during the step of etching said epitaxial layer there are defined anchorages connected to said substrate and elastic elements connecting said body to said anchorages.
16. A method for manufacturing an inertial sensor, comprising:
forming, on a semiconductor substrate, a sample element having a first end coupled to the substrate, the sample element being configured to break under a preselected strain; and
forming, above the semiconductor substrate, a semiconductor material body coupled to a second end of the sample element.
17. The method of claim 16 wherein the sample element has a T shape, the first end forming a cross-bar portion of the T and being coupled to the substrate at extreme ends of the crossbar, the second end extending from a central portion of the crossbar to form the T.
18. The method of claim 16 , further comprising forming an additional sample element having a first end coupled to the substrate, a second end coupled to the semiconductor material body, and configured to break under the preselected strain.
19. The method of claim 16 , further comprising forming a weakened region on the sample element, and wherein the sample element is configured to break at the weakened region under the preselected strain.
20. The method of claim 19 wherein the weakened region comprises a narrowed region of the sample element.
21-28. (canceled)
29. The process of claim 1 , comprising forming, in said sacrificial region, a via over said sample element, and wherein said step of forming the body comprises connecting the body to said sample element through said via.
30. The process of claim 1 wherein said step of forming said sample element comprises forming a plurality of sample elements, of which said sample element is one, and wherein said body is connected to each of said plurality of sample elements.
31. The process of claim 1 , further comprising forming, in said semiconductor wafer, a test circuit configured to detect a break in said sample element.
32. The method of claim 16 , further comprising forming a circuit on the semiconductor substrate, configured to subject the sample element to a voltage such as to cause an electric current to flow through the sample element.
33. The method of claim 32 wherein the circuit is further configured to detect the current flowing in the sample element.
34. A process for the fabrication of an inertial sensor with failure threshold, comprising:
forming, on top of a substrate of a semiconductor wafer, a conductive sample element coupled at a first end thereof to the substrate and shaped so as to be subject to a stress when a second end thereof is outside a relative resting position with respect to the substrate, and wherein the conductive sample element is configured to undergo failure in a controlled way when subjected to a stress of pre-selected intensity; and
forming a body connected to the second end of the sample element.
35. The process of claim 34 , further comprising forming, in the semiconductor wafer, a test circuit configured to detect a change in electrical resistance of the sample element.
36. The process of claim 34 wherein the step of forming a conductive sample element comprises forming a plurality of sample elements of which the sample element is one, each of the sample element being coupled at respective first ends to the substrate and at respective second ends to the body, and each of the sample elements being configured to undergo failure in a controlled way when subjected to the stress of pre-selected intensity.
37. The process of claim 34 wherein the step of forming a sample element comprises the step of making a weakened region of said sample element.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US11/566,590 US7678599B2 (en) | 2002-08-30 | 2006-12-04 | Process for the fabrication of an inertial sensor with failure threshold |
Applications Claiming Priority (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP02425539A EP1394554B1 (en) | 2002-08-30 | 2002-08-30 | Process for the fabrication of a threshold acceleration sensor |
EP02425539.0 | 2002-08-30 | ||
EP02425539 | 2002-08-30 | ||
US10/650,275 US20040121504A1 (en) | 2002-08-30 | 2003-08-27 | Process for the fabrication of an inertial sensor with failure threshold |
US11/566,590 US7678599B2 (en) | 2002-08-30 | 2006-12-04 | Process for the fabrication of an inertial sensor with failure threshold |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/650,275 Continuation US20040121504A1 (en) | 2002-08-30 | 2003-08-27 | Process for the fabrication of an inertial sensor with failure threshold |
Publications (2)
Publication Number | Publication Date |
---|---|
US20070175865A1 true US20070175865A1 (en) | 2007-08-02 |
US7678599B2 US7678599B2 (en) | 2010-03-16 |
Family
ID=31198026
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/650,275 Abandoned US20040121504A1 (en) | 2002-08-30 | 2003-08-27 | Process for the fabrication of an inertial sensor with failure threshold |
US11/566,590 Active 2025-06-21 US7678599B2 (en) | 2002-08-30 | 2006-12-04 | Process for the fabrication of an inertial sensor with failure threshold |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/650,275 Abandoned US20040121504A1 (en) | 2002-08-30 | 2003-08-27 | Process for the fabrication of an inertial sensor with failure threshold |
Country Status (3)
Country | Link |
---|---|
US (2) | US20040121504A1 (en) |
EP (1) | EP1394554B1 (en) |
JP (1) | JP4667731B2 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7678599B2 (en) * | 2002-08-30 | 2010-03-16 | Stmicroelectronics S.R.L. | Process for the fabrication of an inertial sensor with failure threshold |
US20100088061A1 (en) * | 2008-10-07 | 2010-04-08 | Qualcomm Incorporated | Generating virtual buttons using motion sensors |
US20100136957A1 (en) * | 2008-12-02 | 2010-06-03 | Qualcomm Incorporated | Method and apparatus for determining a user input from inertial sensors |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2007298408A (en) * | 2006-04-28 | 2007-11-15 | Matsushita Electric Works Ltd | Electrostatic capacity sensor |
EP2275384B1 (en) * | 2009-07-15 | 2012-02-22 | Nxp B.V. | Threshold acceleration sensor and method of manufacturing |
US9297824B2 (en) * | 2012-09-14 | 2016-03-29 | Intel Corporation | Techniques, systems and devices related to acceleration measurement |
US9222956B2 (en) | 2013-11-26 | 2015-12-29 | Raytheon Company | High bandwidth linear flexure bearing |
CN106076460B (en) * | 2016-06-15 | 2018-04-13 | 亚洲硅业(青海)有限公司 | A kind of device and its application method for handling polycrystalline silicon rod |
US10670825B2 (en) | 2018-08-23 | 2020-06-02 | Raytheon Company | Mounting devices with integrated alignment adjustment features and locking mechanisms |
TWI756860B (en) * | 2020-10-08 | 2022-03-01 | 緯創資通股份有限公司 | Channel structure for signal transmission |
Citations (19)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6508122B1 (en) * | 1999-09-16 | 2003-01-21 | American Gnc Corporation | Microelectromechanical system for measuring angular rate |
US6746891B2 (en) * | 2001-11-09 | 2004-06-08 | Turnstone Systems, Inc. | Trilayered beam MEMS device and related methods |
US20040121504A1 (en) * | 2002-08-30 | 2004-06-24 | Stmicroelectronics S.R.L. | Process for the fabrication of an inertial sensor with failure threshold |
US20040129989A1 (en) * | 2002-08-30 | 2004-07-08 | Stmicroelectronics S.R.I. | Sensor with failure threshold |
US6794728B1 (en) * | 1999-02-24 | 2004-09-21 | Advanced Safety Concepts, Inc. | Capacitive sensors in vehicular environments |
US20040219706A1 (en) * | 2002-08-07 | 2004-11-04 | Chang-Fegn Wan | System and method of fabricating micro cavities |
US20050017313A1 (en) * | 2002-08-07 | 2005-01-27 | Chang-Feng Wan | System and method of fabricating micro cavities |
US20050132814A1 (en) * | 1999-08-20 | 2005-06-23 | Hitachi, Ltd. | Semiconductor pressure sensor and pressure sensing device |
US20050160825A1 (en) * | 2003-12-11 | 2005-07-28 | Proteus Biomedical, Inc. | Pressure sensors having neutral plane positioned transducers |
US7064637B2 (en) * | 2002-07-18 | 2006-06-20 | Wispry, Inc. | Recessed electrode for electrostatically actuated structures |
US20060201248A1 (en) * | 2005-03-11 | 2006-09-14 | Yukihiro Unno | Vibrating gyro element |
US20070101812A1 (en) * | 2005-11-10 | 2007-05-10 | Honeywell International, Inc. | Miniature package for translation of sensor sense axis |
US7350424B2 (en) * | 2002-02-12 | 2008-04-01 | Nokia Corporation | Acceleration sensor |
US20080148847A1 (en) * | 2006-12-20 | 2008-06-26 | Epson Toyocom Corporation | Vibration gyro sensor |
US20080184770A1 (en) * | 2007-02-05 | 2008-08-07 | Epson Toyocom Corporation | Gyro sensor module and angular velocity detection method |
US20080257042A1 (en) * | 2007-01-26 | 2008-10-23 | Epson Toyocom Corporation | Gyro module |
US20080314145A1 (en) * | 2007-06-20 | 2008-12-25 | Epson Toyocom Corporation | Angular velocity detection apparatus |
US7528691B2 (en) * | 2005-08-26 | 2009-05-05 | Innovative Micro Technology | Dual substrate electrostatic MEMS switch with hermetic seal and method of manufacture |
US7545622B2 (en) * | 2006-03-08 | 2009-06-09 | Wispry, Inc. | Micro-electro-mechanical system (MEMS) variable capacitors and actuation components and related methods |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH05142243A (en) * | 1991-11-22 | 1993-06-08 | Omron Corp | Impact sensor and impact sensing device |
JPH08138307A (en) * | 1994-09-16 | 1996-05-31 | Toshiba Corp | Information memory |
DE59603812D1 (en) * | 1996-08-30 | 2000-01-05 | Fraunhofer Ges Forschung | ACCELERATION LIMIT SENSOR |
JPH10270719A (en) * | 1997-03-26 | 1998-10-09 | Mitsubishi Materials Corp | Semiconductor inertia sensor and its production |
JPH11250788A (en) * | 1998-02-27 | 1999-09-17 | Omron Corp | Physical quantity change recording element |
JP2001108703A (en) * | 1999-10-08 | 2001-04-20 | Akebono Brake Ind Co Ltd | Impact detection display member |
DE10005562C2 (en) * | 2000-02-09 | 2002-06-06 | Bosch Gmbh Robert | leveling sensor |
-
2002
- 2002-08-30 EP EP02425539A patent/EP1394554B1/en not_active Expired - Lifetime
-
2003
- 2003-08-27 US US10/650,275 patent/US20040121504A1/en not_active Abandoned
- 2003-08-29 JP JP2003307928A patent/JP4667731B2/en not_active Expired - Lifetime
-
2006
- 2006-12-04 US US11/566,590 patent/US7678599B2/en active Active
Patent Citations (31)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6794728B1 (en) * | 1999-02-24 | 2004-09-21 | Advanced Safety Concepts, Inc. | Capacitive sensors in vehicular environments |
US20050132814A1 (en) * | 1999-08-20 | 2005-06-23 | Hitachi, Ltd. | Semiconductor pressure sensor and pressure sensing device |
US6508122B1 (en) * | 1999-09-16 | 2003-01-21 | American Gnc Corporation | Microelectromechanical system for measuring angular rate |
US6917086B2 (en) * | 2001-11-09 | 2005-07-12 | Turnstone Systems, Inc. | Trilayered beam MEMS device and related methods |
US6746891B2 (en) * | 2001-11-09 | 2004-06-08 | Turnstone Systems, Inc. | Trilayered beam MEMS device and related methods |
US20040188785A1 (en) * | 2001-11-09 | 2004-09-30 | Cunningham Shawn Jay | Trilayered beam MEMS device and related methods |
US20070158775A1 (en) * | 2001-11-09 | 2007-07-12 | Wispry, Inc. | Methods for implementation of a switching function in a microscale device and for fabrication of a microscale switch |
US6876482B2 (en) * | 2001-11-09 | 2005-04-05 | Turnstone Systems, Inc. | MEMS device having contact and standoff bumps and related methods |
US6876047B2 (en) * | 2001-11-09 | 2005-04-05 | Turnstone Systems, Inc. | MEMS device having a trilayered beam and related methods |
US7350424B2 (en) * | 2002-02-12 | 2008-04-01 | Nokia Corporation | Acceleration sensor |
US7299538B2 (en) * | 2002-07-18 | 2007-11-27 | Wispry, Inc. | Method for fabricating micro-electro-mechanical systems |
US7064637B2 (en) * | 2002-07-18 | 2006-06-20 | Wispry, Inc. | Recessed electrode for electrostatically actuated structures |
US20050017313A1 (en) * | 2002-08-07 | 2005-01-27 | Chang-Feng Wan | System and method of fabricating micro cavities |
US20040219706A1 (en) * | 2002-08-07 | 2004-11-04 | Chang-Fegn Wan | System and method of fabricating micro cavities |
US6858810B2 (en) * | 2002-08-30 | 2005-02-22 | Stmicroelectronics S.R.L. | Sensor with failure threshold |
US20040121504A1 (en) * | 2002-08-30 | 2004-06-24 | Stmicroelectronics S.R.L. | Process for the fabrication of an inertial sensor with failure threshold |
US20040129989A1 (en) * | 2002-08-30 | 2004-07-08 | Stmicroelectronics S.R.I. | Sensor with failure threshold |
US20050160827A1 (en) * | 2003-12-11 | 2005-07-28 | Proteus Biomedical, Inc. | Pressure sensors having transducers positioned to provide for low drift |
US20050160825A1 (en) * | 2003-12-11 | 2005-07-28 | Proteus Biomedical, Inc. | Pressure sensors having neutral plane positioned transducers |
US20050160826A1 (en) * | 2003-12-11 | 2005-07-28 | Proteus Biomedical, Inc. | Pressure sensors having stable gauge transducers |
US20050160824A1 (en) * | 2003-12-11 | 2005-07-28 | Proteus Biomedical, Inc. | Pressure sensors having spacer mounted transducers |
US20050160823A1 (en) * | 2003-12-11 | 2005-07-28 | Proteus Biomedical, Inc. | Implantable pressure sensors |
US20060201248A1 (en) * | 2005-03-11 | 2006-09-14 | Yukihiro Unno | Vibrating gyro element |
US7528691B2 (en) * | 2005-08-26 | 2009-05-05 | Innovative Micro Technology | Dual substrate electrostatic MEMS switch with hermetic seal and method of manufacture |
US7467552B2 (en) * | 2005-11-10 | 2008-12-23 | Honeywell International Inc. | Miniature package for translation of sensor sense axis |
US20070101812A1 (en) * | 2005-11-10 | 2007-05-10 | Honeywell International, Inc. | Miniature package for translation of sensor sense axis |
US7545622B2 (en) * | 2006-03-08 | 2009-06-09 | Wispry, Inc. | Micro-electro-mechanical system (MEMS) variable capacitors and actuation components and related methods |
US20080148847A1 (en) * | 2006-12-20 | 2008-06-26 | Epson Toyocom Corporation | Vibration gyro sensor |
US20080257042A1 (en) * | 2007-01-26 | 2008-10-23 | Epson Toyocom Corporation | Gyro module |
US20080184770A1 (en) * | 2007-02-05 | 2008-08-07 | Epson Toyocom Corporation | Gyro sensor module and angular velocity detection method |
US20080314145A1 (en) * | 2007-06-20 | 2008-12-25 | Epson Toyocom Corporation | Angular velocity detection apparatus |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7678599B2 (en) * | 2002-08-30 | 2010-03-16 | Stmicroelectronics S.R.L. | Process for the fabrication of an inertial sensor with failure threshold |
US20100088061A1 (en) * | 2008-10-07 | 2010-04-08 | Qualcomm Incorporated | Generating virtual buttons using motion sensors |
US8682606B2 (en) | 2008-10-07 | 2014-03-25 | Qualcomm Incorporated | Generating virtual buttons using motion sensors |
US20100136957A1 (en) * | 2008-12-02 | 2010-06-03 | Qualcomm Incorporated | Method and apparatus for determining a user input from inertial sensors |
US8351910B2 (en) * | 2008-12-02 | 2013-01-08 | Qualcomm Incorporated | Method and apparatus for determining a user input from inertial sensors |
Also Published As
Publication number | Publication date |
---|---|
JP4667731B2 (en) | 2011-04-13 |
EP1394554B1 (en) | 2011-11-02 |
JP2004134763A (en) | 2004-04-30 |
EP1394554A1 (en) | 2004-03-03 |
US7678599B2 (en) | 2010-03-16 |
US20040121504A1 (en) | 2004-06-24 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US7678599B2 (en) | Process for the fabrication of an inertial sensor with failure threshold | |
US6858810B2 (en) | Sensor with failure threshold | |
US10626008B2 (en) | Micro-electro-mechanical device and manufacturing process thereof | |
US8186221B2 (en) | Vertically integrated MEMS acceleration transducer | |
US6146917A (en) | Fabrication method for encapsulated micromachined structures | |
US5417111A (en) | Monolithic chip containing integrated circuitry and suspended microstructure | |
US8569092B2 (en) | Method for fabricating a microelectromechanical sensor with a piezoresistive type readout | |
EP0762510B1 (en) | Method for fabricating a monolithic semiconductor device with integrated surface micromachined structures | |
US7322242B2 (en) | Micro-electromechanical structure with improved insensitivity to thermomechanical stresses induced by the package | |
US5620931A (en) | Methods for fabricating monolithic device containing circuitry and suspended microstructure | |
US7368312B1 (en) | MEMS sensor suite on a chip | |
US6829937B2 (en) | Monolithic silicon acceleration sensor | |
CN103373697B (en) | Hybrid integrated component and method for the manufacture thereof | |
US7633131B1 (en) | MEMS semiconductor sensor device | |
EP2871456A1 (en) | Pressure sensor | |
US20160209344A1 (en) | Complex sensor and method of manufacturing the same | |
US20210257539A1 (en) | Semiconductor Strain Gauge and Method for Manufacturing Same | |
CN109341932B (en) | Pressure sensor chip and manufacturing method thereof | |
JP2822486B2 (en) | Strain-sensitive sensor and method of manufacturing the same | |
US20050132803A1 (en) | Low cost integrated MEMS hybrid | |
KR100238999B1 (en) | Semiconductor micromachining method | |
JP2006214963A (en) | Acceleration sensor, electronic equipment, and manufacturing method for acceleration sensor | |
JPH11219643A (en) | Micro mechanical switch and its manufacture | |
CN115014593A (en) | Preparation method of pressure sensor and pressure sensor | |
JPH10132850A (en) | Semiconductor acceleration sensor |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
STCF | Information on status: patent grant |
Free format text: PATENTED CASE |
|
FPAY | Fee payment |
Year of fee payment: 4 |
|
MAFP | Maintenance fee payment |
Free format text: PAYMENT OF MAINTENANCE FEE, 8TH YEAR, LARGE ENTITY (ORIGINAL EVENT CODE: M1552) Year of fee payment: 8 |
|
MAFP | Maintenance fee payment |
Free format text: PAYMENT OF MAINTENANCE FEE, 12TH YEAR, LARGE ENTITY (ORIGINAL EVENT CODE: M1553); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY Year of fee payment: 12 |